const map1 = new Map();
map1.set('a', 1);
map1.set('b', 2);
map1.set('c', 3);
map1.set(undefined, null);
map1.set(null, undefined);
map1.set(NaN, { a: 1, b: "hello" });
console.log(map1.get('a'));
console.log(map1.get(undefined));
console.log(map1.get(null));
console.log(map1.get(NaN));
map1.set('a', 97);
console.log(map1.get('a'));
console.log(map1.size);
map1.delete('b');
console.log(map1.size);
